Interpretive Summary: For over a decade evidence has mounted that increasing atmospheric greenhouse gas concentration is resulting in climate change, particularly increased temperature. Under the Kyoto Protocol of the United Nations Framework Convention on Climate Change, signatory countries must decrease emissions of carbon dioxide to the atmosphere, or increase rates of removal and storage. The Protocol’s Clean Development Mechanism (CDM) allows a country that emits carbon above agreed-upon limits to purchase carbon offsets from an entity that uses biological means to absorb or reduce greenhouse emissions. The CDM is currently offered for afforestation and reforestation projects, but may apply subsequently to sequestration in agricultural soils. Markets outside of Protocol are developing for soil carbon sequestration. There is great interest in C sequestration as a mechanism to provide enhanced productivity, income and food security benefits, and conservation of natural resources in the developing world, including semiarid agroecosystems. This special issue of Agricultural Systems was developed to provide an overview of technological and institutional innovations that would be required to make C markets work for the rural poor in Africa’s Sudan-Sahelian region. The papers consider the potentials, as well as the challenges involved, from biophysical, social, economic, cultural, and political perspectives. The articles in this issue indicate that some potential exists for C sequestration and trade in West African drylands, but that to make those promises a reality, more research and practical experiences are needed to understand and overcome uncertainties, streamline processes, create efficiencies, minimize transaction costs and reduce risks at technical, infrastructural, economic, social and institutional levels of C sequestration and trading.

Technical Abstract:
For over a decade evidence has mounted that increasing atmospheric greenhouse gas concentration is resulting in climate change, particularly increased temperature. Under the Kyoto Protocol of the United Nations Framework Convention on Climate Change, signatory countries must decrease emissions of carbon dioxide to the atmosphere, or increase rates of removal and storage. The Protocol’s Clean Development Mechanism (CDM) allows a country that emits carbon above agreed-upon limits to purchase carbon offsets from an entity that uses biological means to absorb or reduce greenhouse emissions. The CDM is currently offered for afforestation and reforestation projects, but may apply subsequently to sequestration in agricultural soils. Markets outside of Protocol are developing for soil carbon sequestration. There is great interest in C sequestration as a mechanism to provide enhanced productivity, income and food security benefits, and conservation of natural resources in the developing world, including semiarid agroecosystems. This special issue of Agricultural Systems was developed to provide an overview of technological and institutional innovations that would be required to make C markets work for the rural poor in Africa’s Sudan-Sahelian region. The papers consider the potentials, as well as the challenges involved, from biophysical, social, economic, cultural, and political perspectives. The articles in this issue indicate that some potential exists for C sequestration and trade in West African drylands, but that to make those promises a reality, more research and practical experiences are needed to understand and overcome uncertainties, streamline processes, create efficiencies, minimize transaction costs and reduce risks at technical, infrastructural, economic, social and institutional levels of C sequestration and trading.